6 you should be able to drill out from the top with right hand drill bit or twist off the head first and drill out on the bench. It of course will be easier to repair with the housing removed.

A recent thread with same job involved the 7 or 8 getting striped in the head, repair was using a longer bolt as the threading goes father in the head than the stock bolt.

If you drill out 80% of the 6 bolt it should weaken it to turn it out from the head.

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)